Lifting of hydrocarbons from oil fields involves introducing into the well a casing that extends down sufficiently to reach the hydrocarbon-containing strata, so that any oil, gas and water found therein may flow upwardly to the surface through the casing to be then separated, stored or channeled to its next destination. The oil, gas and water from the strata enter the casing and, because of their different densities, they segregate from each other so that water remains at the bottom of the casing, while oil floats over it and gas flows up through the casing.
Conventional oil lifting requires the use of pumping units disposed on the surface of the field ground and on the wellhead, which include, among other components used for fluid extraction, a pump lever, a suction rod and a pump placed downhole within the casing at the deepest possible production position. For operating the suction rod, its lower end is connected to the pump, while its upper end is connected to the pump lever disposed on the ground surface. By means of a mechanical arm lever, the pump lever drives the upwards and downwards reciprocating movement of the suction rod, thus performing the pumping work in the production well.
Another widely known type of pumping system consists in using a bailing system disposed on the ground surface adjacent to the production well, using a bailer mechanism disposed on the ground surface adjacent to the production well, comprising a bailer type (tube and hose) system, a pulling strip or cable which extends along an admission tube or arm, and a hoist mechanism. In this system for lifting hydrocarbons, the bailing system is operated by spooling and unspooling a pulling cable from a hoisting mechanism, to which one end of the wireline is attached, while the other end is attached to the upper end of the bailer-type mechanism placed within the well casing. During operation of the hoist mechanism by spooling and unspooling the wireline or cable, the latter makes a reciprocating movement and undergoes considerable stresses when it is spooled to lift the bailer or unspooled for lowering it to the oil-containing section of the well casing. When the bailer is submerged into the oil-containing section, it collects some oil and gets filled with it. Then, the bailer is lifted up to the surface and the oil is poured into a storage dam.
In these conventional systems for lifting hydrocarbons, fluid discharge from the hose that extends along the borehole is achieved by the action of gravity. These systems have disadvantages that must be overcome. In fact, during the lowering operation, the hose may stick to the tube due to the presence of viscous or paraffin hydrocarbons. These conditions may be affected by external temperatures and the tubes may be worn off by friction with the hose, which may cause ecological damage. In addition, the hose must have thicker walls in order to withstand the strain caused by the rollers over the curvature of the header when entering into the PVC tube. Furthermore, the hose diameter is limited by the header's entrance hole and the recovery capacity of the hose is limited by the length of the tubes, all of which leads to a reduction in productivity. Another disadvantage is that the hose detection system is external and has no protection. In addition, harsh environmental conditions (temperatures, wind, sunlight), the presence of animals, mishandling, etc. can damage the tube joints and cause leaks. The presence of gas pockets may damage PVC tubes and cause environmental damage. In addition, the horizontal tube where the fluid is discharged is made of plastic and can only withstand low gas pressure. Consequently, the gas cannot be transferred by its own pressure and requires permanent venting.
In order to solve the above mentioned drawbacks of conventional hydrocarbon-lifting facilities, the inventors have developed the arrangement of the present invention, which provides outstanding improvements over the prior art. In fact, the arrangement to be used in oilfield wells for lifting hydrocarbons is capable of capturing gas from the well and thus avoid venting, which increases productivity of the lifting equipment. One of the most important factors favoring productivity is the use of the gas pressure from inside the casing for draining the hose. The hose length may be made proportional to gas pressure at a ratio of 10 ml per 1 kg/sq. cm. of gas pressure, without modifying the length of the surface equipment. In addition, there will be less tubing on the surface and all the moving elements of the arrangement will remain within the casing, thus avoiding possible leaks of fluid at surface level and providing greater safety to the lifting process. It should also be underlined that equipment, mounting and operation costs are lower than those of conventional arrangements, no “pulling” is needed, it is easily maintained and consumes less power, among other advantages.